Production of aryl thiols



Patented June 25, 1946 UNITED 'rnonuo'rion or ARYL THIOLS Wilbur A.Lazier, New Castle County, and Frank K..8lgnaigo, Wilmington, De1.,assignors tell. I. du Pont de Nemours & Company, Wilmington, Dei., acorporation of Delaware No Drawing. Application October 31, 1940, SerialNo. 383,680

This invention relates to a process for the production of aryl thiolsand. more particularly, to the production of aryl thiols from arylsulfonic and sulfinic acids and their derivatives.

This application is a continuation-in-part of our copending applicationSerial No. 289,582 tiled August 11, 1939, matured as Patent No.2,221,804 issued November 19, 1940. In this copending application wedescribed a process for catalytically hydrogenating aromatic compoundscontaining an oxygen-sulfur group in which the sulfur atom is directlyattached to a carbon atom in the aromatic group. By this process amixture of organic oxygen-free sulfur compounds and hydrocarbons wereobtaineid. This invention represented a marked advance in the field oicatalysis of sulionic compounds because prior to said invention suchreactions were thought to be impossible. Through further extensiveresearch we have found that under selected conditions it is possible to'obtain aryl thiols in high yields to the practical exclusion ofaromatic hydrocarbons when catalytically hydrogenating aromaticoxygen-sulfur compounds. g

This invention has as its object the preparation of aryl thiol by a newand improved method. Another object is to provide a simple practicalcatalytic method for preparing aryl thiols from readily accessiblematerials. Other objects will be apparent from the following descriptionof the invention.

Thes objects are accomplished by the follow- 14 Claims. (Cl. 260-609)the base metal sulfide hydrogenation catalysts,

and in the presence or hydrogen sulfide. The temperature of carrying outthe reaction should be at or near the minimum temperature needed foreflecting hydrogenation. This minimum temperature will vary within the.range stated depending upon the material being hydrogenated. Thepresence of hydrogen sulfide has been found to be exceptionallybeneficial as it suppresses side reactions and increases theeiiectivenes or the catalyst.

The exact manner of practicing thlsinvention will vary depending uponthe particular compound processes as shorwn'by the following exam- 2pies. The quantity of materials referred to in these examples isexpressed as parts by weight.

Example 1 Into a high pressure autoclave there was charged l parts ofp-toluenesulfonanilide, 100 parts of decalin and parts of a suliactivecatalyst prepared by treating a methanol suspension of finely dividedpyrophoric cobalt with hydrogen sulfide at room temperature until nofurther sulfidation occurs. Hydrogen was then forced into the autoclaveto a pressure or about 1500 lbs. per sq. in. and the autoclave wasagitated and heated to a temperature 01' 275 C. at a pressure of 3000lbs. per sq. in. After four hours heating the autoclave was cooled andthe contents were illtered to remove the catalyst. Nitrogen was thenblown through the solution to remove the hydrogen sulfide formed and analiquot of the solution was titrated with standard iodine solution. Theamount of iodine absorbed indicated that only traces of thiocresol wereformed. By distillation, there was obtained 23 parts of toluene and ahigher boiling fraction consisting of a mixture of aniline and thedecalin solvent.

The above experiment was repeated using the same reactants and sameconditions except that the autoclave was heated to a temperature of 250C. for 8 hours. On working up the reaction mixture as described in thepreceding paragraph, it

was found to contain p-thiocresol in an amount Enamrle ll Sixty-fiveparts of sodium p-toluenesulfinate dihydrate and parts of sulfur werecharged into a hydrogenation autoclave together with parts of water and8 parts of cobalt polysulfide catalyst prepared by precipitating anaqueous solution of cobalt chloride with a solution 0! an equivalentamount of sodium trisulfide. The autoclave was charged with hydrogen toan initial pressure of 500 lbs. per sq. in. and agitated and heated atC. A rapid reaction occurred as 3 evidenced by the decrease in pressure,and additional hydrogen was added from time to time to replace thatabsorbed. the total pressure being maintained within the range from 500to 1000 lbs. per sq. in. After 2.5 hours at 175 C. no further pressuredrop was observed and the autoclave was heated for an additional hour toinsure completion of the reaction. The contents of the cooled autoclavewere rinsed out with water, filtered from the catalyst and acidifiedwith dilute sulfuric acid. The acidified mixture was then extracted withether and the extract was fractionally distilled. After the ethersolvent was removed 30 parts of pure p-thiocresol distilled at 67 C. at7 mm. pressure. The yield was 80% of the theoretical. This hydrogenreduction may be formulated as follows:

- Catalyst (HICQHiBmNa 2H. v CHiClHlSNa 211,0

Catalyst S H: -0 H18 The above experiment was repeated under identicalconditions except that 6 parts of finely divided pyrophoric iron wassubstituted for the cobalt polysulfide catalyst. The iron was preparedby extracting the aluminum with boiling caustic alkali from a finelyground alloy of equal weights of iron and aluminum. During the period ofheating the autoclave up to reaction temperature the finely divided ironreacted with some of the sulfur forming an active iron sulfide catalyst.The product was isolated as described above and pure p-thiocre'sol wasobtained in 84% yield.

Example HI Sixty-five parts of sodium benzenesulfinate dihydrate wascharged into a hydrogenation autoclave together with'20 parts of sulfur,100 parts ofwater, and 7 parts of nickel polysulfide catalyst preparedas described under Example II for the cobalt polysulfide catalyst exceptthat an I 0x01 15010] NarSO;

and acidified with dilute sulfuric acid. The solid thio-beta-naphtholwhich separated was filtered from the mixture and dried. Analysis of thematerial indicated it to contain 94% of thicbeta-naphthol. The yield was21 parts, corresponding to 80% of the theoretical. The formation ofthio-beta-naphthol may be formulated as follows:

2Na0H --0 010111 OINB NaaSO. NaCl m0 Cat. (2) CmHrBOgNB 2H: Y; CloH1SNa21110 Example V and blown with nitrogen to remove the hydrogen sulfide.Titration of an aliquot of the solution with standard iodine solutionindicated the presence of 3.7 parts of pthiocres'ol. By fractionaldistillation the p-thiocresol was separated from the solvent, phenol andunconverted starting material. The distillation residueconsisted of 45parts of unconverted phenyl p-toluenesulfonate. The conversion of theester to the thiol was 12%. The yield, however, based on unreequivalentamount of nickel chloride was substituted for the cobalt chloride. Theautoclave was charged with hydrogen to an initial pressure of 1100 lbs.per sq. in. and heated at a temperature of 175 C. for 3.5 hours.Additional hydrogen was added from time to time to replace thatabsorbed, the total pressure being maintained within the range from 1100to 2500 lbs. per sq. in. The contents of the cooled autoclave were thenfiltered from the catalyst and acidified with dilute sulfuric acid. Theoil which separated was taken up in benzene and fractionally distilled.After removal of a foreshot of benzene, 30 parts of pure thiophenoldistilled at 84 C. at mm. The yield was of the theoretical.

Example IV Thirty-six parts of beta-naphthalene'sulfone chloride wasadded with stirring to a solucovered starting material was 83%. Thehydrogenation of the sulfonate to thiocresol may be formulated asfollows:

Catalyst omclmsoicdn n. -o

cmcsmsn canon 211.0

Example VI Thirty-three parts of crude sodiumbetsnaphthalenethiosulfonate. prepared by reactingbeta-naphthalenesulfone chlorine with sodium sulfide, was charged into ahydrogenation autoclave together with 24 parts of sodium sulfidenonahydrate, parts of water and 7 parts of cobalt sulfide catalystprepared as described in Example 11. The autoclave was charged withhydrogen at superatmospheric pressure and heattion of 21 parts of sodiumsulfite in 80 parts of water at 80 C. The solution was maintained Justalkaline by the addition of sodium hydroxide as ed at C. under a totalpressure of 2500 lbs. per sq. in. for four hours. After this period theautoclave was cooled and the product was filtered from the catalyst,acidified. and extracted with benzene. Evaporation of the benzeneyielded a tight tan colored solid residue of the thio-betanaphthol of87% purity. These reactions may be formulated as follows:

7 1011180101 U uHrBOaBNa 8 Example VII autoclave were then filtered fromthe catalyst 16 tion mixture was then rinsed out with ether, filmixtureyielded 18 parts of pure thiophenol boil-- at as c. at 49 mm. Thistransformation is in: represented by the following equation: 1

Catalyst CoHJSOaH 2H EEO C'HSH 2H) Example VII I A mixture of 440 partsof sodium monosulfide nonahydrate, 04 parts of sulfur, and 100 parts ofsodium beta-naphthalenesuifonate were fused in an iron pot equipped withan agitator. The temperature was slowly raised during the course of fourhours to 350 C. and maintained there for an additional hour. The cooledsolid product was dissolved in 300 parts of hot water. The aqueousmixture was then charged into a hydrogenation autoclave together with 36parts of sulfur, 90 parts of benzene, and 18 parts of finely dividediron prepared by extracting the aluminum with boiling caustic alkalifrom a finely ground alloy of equal weights of iron and aluminum. Theautoclave was charged with hydrogen at superatmospheric pressure andheated at 225 C. for 5 hours. Additional hydrogen was added occasionally to replace that absorbed, the total pressure being maintainedwithin the ran e from 1800 to 2500 lbs. per sq. in. The cooled reactionmixture was then filtered from the catalyst, acidi fied with dilutesulfuric acid, and extracted with benzene. Evaporation of the benzeneextract yielded a residue consisting of crude solid thionaphthol.

. In the foregoing examples the hydrogenation to thiols of certainspecific aromatic sulfur-oxygen compounds has been disclosed forpurposes of illustration. The process of this invention is not limitedto these particular materials, however, but is applicable generally toaromatic sulfinic acids, sulfonic acids and substances bydrolyzable tothese acids such as the salts, alkyl or aryl esters, amides, alkyl oraryl substituted amides, anhydrides, and acid halides. In addition tomaterials of this type. the process of this invention is also applicableto the thio analogs of these materials; 1. e., compounds in which one ormore of the oxygen atoms in the sulfur-oxy-' gen group have beenreplaced by sulfur. Com- ,pounds of this class include the thiosulfinicacids and substances hydrolyzable to these acids (e. g., RSzOH, RBzONa)and the thiosulfonic acids and substances hydrolyzable to these acids100 to 300 C. and at pressures ranging from atmospheric to a'maximumdetermined by the practical limitations of the reaction vessel. Usually,however, it is preferred to carry out the reaction at a temperaturewithin the range from 125 to 250 C. when a sulfinic acid, thiosulfinicacid, thiosulfonic acid'or a derivative of such acid is being processedand at temperatures ranging from 1'75 to 300 C. when a sulfonic acid orderivative thereof is being processed. It is especially desirable tooperate at the minimum temperature at which reaction will proceed whenthis genated to hydrogen sulfide at an early stage in l is above 200 C.The preferred pressure range is 100 to 4000 lbs/sq. in. and the totalpressure should be in excess of the partial pressure of the reaction. Itis possible that the improved results obtained using hydrogen sulfide inthe reaction medium are brought about by at least partial substitutionof the oxygen atoms in the sulfur-oxygen group by sulfur, therebyforming thiosulfinic or thiosulfonic derivatives. I Such compoundsapparently undergo hydrogenation more rapidly and at a lower temperaturethan (e. 8., RSaOaH, RSsOI-I, RSzOzK, RSrONI-IR',

RSOz-(Sh-SOaR).

The aromatic nuclei of the compounds falling within the scope of thisinvention may be those of the simple aromatic hydrocarbons suchasbenthat these values may be varied within the scope of this inventionsince the optimum conditions depend somewhat upon the particularcompound treated. In general, the processes of this invention areoperable at temperatures ranging from the corresponding oxygenderivatives. We do not wish, however, to be limited by theseconsiderations.

The process may be carried out in the absence of solvents although moreusually it is convenient to use a solvent. Examples of solvents that maybe employed are water or organic solvents as, for example, alcohols,ethers, hydrocarbons, and the like. Other materials such as alkalies,mineral or organic carboxylic acids, acid anhydrides, ammonia, or aminesmay also be pres ent in the reaction media if desired.

The proportion of catalyst may be varied considerably. In general, anamount of catalyst equal to 2 to 15% by weight of the starting materialwill bring about reaction at a suitable rate. The type of catalyst usedmay likewise be varied considerably but in general the sulfides orpolysulfides of the common hydrogenating metals are effective. Asexamples of metal sulfide catalysts that may be used are sulfides orpolysulfides of copper, silver, lead, maganese, iron, cobalt, nickel,molybdenum, tungsten, or combinations of such sulfides. It is preferredto use as catalysts, sulfides of iron, cobalt, nickel, or molybdenumsince these have been found to be especially active for thehydrogenation of aryl sulfur-oxygen compounds. Catalysts of the abovetype are referred to herein as sulfactive hydrogenation catalysts. Themethod of preparation of representative: sulfactive catalysts isindicated in the foregoing: examples. In general, metal sulfides may beformed by precipitation methods or by sulfidation ofthe metals or theircompounds at ordinary or elevated temperatures by means of sulfur, hydrogen sulfide, or other volatile sulfur compounds. The activity ofcertain of the metal fide catalysts may be improved by treatment withuse of the catalyst for the hydrogenation reuctioni Finely dividedmet-cl sulfides may be used as such or they moy be supported on.suituble ccrriers such as kieseiuuhr, magnesia, or alumina.

- The catalytic hydrogenation of aromatic cui fur-oxygen compounds cornin some cases ad -mm tcgeously' be employed in conjunction with chem=icui reduction methods us has been described in Ema-cl nics IV, Vi endH11. Hence it is s. pert of this invention to prc-treet aromaticsulfurwuy gen compounds with chemical reducing agents and tosubsequently continue the reduction to the trust stage by catalytichydrogenation as disclosed herein. Examples of chemical reducing scentsthat may be used in this connection are electro negative metals inccuiuucticu with substunces her ing u replaceable hydrogen storm is.No+slcchoL Zn+oike.li hydrogen sulfide, mluole mete sulfides endpolysulfides, sulfur, sulfur dioxide, sulfites, hyposulfites,tiiiosuiiotes end the like.

This invention is useful for the prepuretionoi eryl thiols which arevaluabl products having many industrial uses as, for example, rubberchemicals, insecticides and dycstuii" intermediates.

This inventionlofiers many advantages over older processes for preparingeryl thiolsit com prises a, novel and eflective cctolytic hydrogenw tionprocess by which aromatic sulfur-oxygen compounds are converted by esingle operation into oryl thlols.

It is apparent that many widelydifierent em bodimcnts of thisinveutioumuy be made without departing from the spirit and scope thercotand therefore it is not intended to be limited ex cept as indicated inthe appended claims.

We claim: 1

l. The process for producing 'an uryl thiol which comprisescatalyticully hydrogenating the oxygenated sulfur group of a compound ofthe class consisting of aryl sulfonic acids, sulfinic acids, the thioanalogs of these acidsancl substances hydrolyzable to said aryl sulfonicand sulfmic acids and their thio analogs, at a. temperature between100and 300 C.

' 2. Theprocess for producing an uryl thicl which comprisescatalyticaily hydrogenating in the presence of hydrogen sulfide theoxygenated sulfur group of o-compound of the class consisting of arylsulfonic acids, sulflmc acids, the thio analogs these acids andsubstances hydrolyz-.

active catalyst the oxygenated culmigroup oi a. compound oi the classconsisting or cry)! sulfonic acids, sulflnic acids, the thio analogs ofthese acids and substances hydrolyzable to said aryl hydrogen atelevated temperetwes. The use sulfinic acid. I ll. The process forproducing thio-beta-naphcuifonic end suliinic acids and their thioanalogs, at as temperature between il0cud 369 C.

d. The process of cluim 3 in which the sulfactive catalyst is is basemetal sulfide.

The process of claim 3 characterised inthct the tcrcpercture ismaintained at about the minimum temperature for eflectizig the catalyticre action.

8. The process for producing thionapiitlools which compriseshydrogeneting the oxygenated sulfur group of compounds of the classconsisting of naphthalene suiicnic acids, sulflnic acids, the

thio analogs of said acids, and substances hydrolyzshie to soici or yisulfonic cud suidnic acids and their this enclose, in the presence oi asbase metui sulfide catalyst and sit s temperature oi be tween we and 3%52.

'3. The process for producing: on eryl thioi which comprisescotslyticcily hydrogenuting in the presence of hydrogen sulfide e. saltoi-en cryi suliinic ecirl in the presence or" o base metal sul= fideceteiyst st temperature of 125 to 259 i3.

8. The process for producing; an cry! tiiici which compriseshydrcgcncting the oxygenated sulfur group or" 5 compound of the classconsisting of oryl sulfonic acids, suliinic acids, the table onologsofthese acids, and substances hydrolyzable' to seid oryl sulfonic andsulfinic acids and 1 their thio analogs in the presence of a. suliactivecatalyst comprising a. sulfide of a metal of the group consisting ofiron, cobalt, nickel and molybdenum, at u temperature between and 300 C.i

ii. The process for producing an aryl thiol which comprisescatalytically hydrogenoting a substance of the class consisting of arylthiosulionic acids, eryl thlosuli'inic acids, and substanceshydrolyzuble to said oryl thiosulfonic and thio= sulfinic acids in thepresenceoi a base metal sultid catalyst, at 9. temperature between 100and sec" C.

- iii. The process of claim 7 in which the salt oi an oryi sulfluic acidis a salt of beta-naphthalenethol which comprises reactingbeta-naphthalenesulfoue chloride with sodium'sulflte and sodiumhydroxide and thereafter cctalytically hydrogenctlug the reactionproduct in the presence of hydrogen sulfide and a sulfactivemetahsuiflde catalyst at a temperature of from to 253" C.

12. The process of claim 11 in which the metal sulfid is an ironsulfide.

13. The process of claim 9 in which the compound hydrogenated isselected-from the class of salts oi aryl thlosulionic acids and arylthiosub finic acids.

. 14. The process for producing an aryl thiol g which comprisescatclytically lwdrozenating on aryl sulflnlc acid in the presence orhydrogen sulfide and abase metal sulfide catalyst at a temperature of125 C. to 250 C.

WILBUR A. LAZIER. FRANK K. SIGNAIGO.

